System for stopping sewing machine needle at predetermined position

ABSTRACT

A system having means for automatically stopping the needle of an electric sewing machine at an upper or lower position in response to the stoppage of the machine during or upon completion of the sewing operation. After the stoppage, the needle can be moved to the other position and stay there by the manipulation of a change-over switch. Also, by the manipulation of a push-button switch, the needle can be stopped at such position after effecting one or more stitches at low speed. Another switch is further provided so as to cut off the needle stopping means from the power supply and stop the needle at any desired position instead of the stopping operation by the needle stopping means.

United States Patent 91 Soeda SYSTEM FOR STOPPING SEWING v MACHINE NEEDLE AT PREDETERMINED POSITION [75] Inventor:

[73] Assignee: Yamamoto Electric Industrial Co.

Ltd., Sukagawa-shi, Japan [22] Filed: May 10, 1971 [21] Appl. No.: 141,733

Katsuji Soeda, Sukagawa, Japan [30] Foreign Application Priority Data 51 Jan.29, 1974 FOREIGN PATENTSOR APPLICATIONS 1,174,013 12/1969 Great Britain .1 112/219 A 57 ABSTRACT A system having means for automatically stopping the needle of an electric sewing machine at an upper or lower position in response to the stoppage of the machine during or upon completion of the sewing operation. After the stoppage, the needle can be moved to the other position and stay there by the manipulation of a change-over switch. Also, by the manipulation of a push-button switch, the needle can be stopped at such position after effecting one or more stitches at low speed. Another switch is further provided so as to cut off the needle stopping means from the power supply and stop the needle at any desired position instead of the stopping operation by the needle stopping means.

3 Claims, 2 Drawing Figures SYSTEM FOR STOPPING SEWING MACHINE NEEDLE AT PREDETERMINED POSITION BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to electric sewing machines provided with a commutator motor which is driven by an a.c. power supply and whose speed is controlled by controlling the gate current supplied to a silicon controlled rectifier connected in series therewith. More particularly, this invention relates to improvements in a system for automatically stopping the sewing needle at a predetermined position in response to the stoppage of the machine during or upon completion of the sewing operation.

2. Description of the Prior Art Various systems for automatically stopping the sewing needle of an electric sewing machine at a predetermined position have been proposed heretofore. A known system of this kind has been defective in that turning of the flywheel by the hand of a sewer for the purpose of effecting initial winding of a thread to the bobbin of the sewing machine with the machine results in actuation of the needle stopping unit thereby causing the rotation of the motor and thus imparts a feeling of unrest to the sewer.

SUMMARY OF THE INVENTION It is therefore a primary object of the present invention to provide an improved system of the kind above described which obviates the trouble heretofore encountered.

Another object of the present invention is to provide a system for use in an electric sewing machine in which means are provided for automatically stopping the needle at a predetermined position such as, for example, an upper or lower position instead of an intermediate position in response to the stoppage of the sewing machine during or upon completion of the sewing operation with the machine.

A further object of the present invention is to provide a system of the above character in which a change-over switch and a push-button switch are provided so that actuation of these means can also cause the needle to stop at the upper or lower position.

Another object of the present invention is to provide a system of the above character in which another switch is provided so that, when this switch is urged to one of the two positions, turning of the flywheel by hand does not actuate the needle stopping unit which is therefore cut off from the system and the needle can be stopped at any desired position instead of the stopping operation by the needle stopiing unit.

The above and other objects, features and advantages of the present invention will be apparent from the following detailed description taken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a circuit diagram of a preferred embodiment of the present invention.

FIG. 2 is a graph showing the relation between the operating characteristic of a neon lamp and the gatecathode voltage of a silicon controlled rectifier.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to F IG..1, a commutator motor M includes a permanent magnet field system PM, an armature A, and a pair of brushes B, and B in contact with the armature A. The brush B, is connected with a neon lamp N, and with one of the a.c. power supply terminals E, through a terminal a of a terminal block 1. A series circuit of a resistor R,, a variable resistor VR, and a resistor R is connected across the brushes B, and 13,, and the movable arm of the variable resistor V-R, is connected to the gate of a silicon controlled rectifier SCR by a series circuit of a trimmer resistor VR a resistor R and a rectifier SR,. The junction point of the resistor R and the rectifier SR, is connected with a terminal 0 of the terminal block 1.

A parallel circuit of a capacitor C and a resistor R is connected across the gate and cathode of the silicon controlled rectifier SCR, and a varister V is connected across the anode and cathode of the silicon controlled rectifier SCR. Further, the cathode of the silicon controlled rectifier SCR is connected with the brush 8,, while the anode thereof is connected with a terminal e of the terminal block 1 through a main switch SW,. THis main switch SW, turns on and off the power supplied to the control circuit. The terminal e is in turn connected with the other a.c. power supply terminal E The brush B, is connected with the anode of the silicon controlled rectifier SCR through a series circuit of a resistor R 21 rectifier SR and a capacitor C The resistor R acts to prevent an impulse current from being applied to the capacitor C,. The junction point of the rectifier SR and the capacitor C, is connected with a terminal b of the terminal block 1 through resistors R and R7.

A needle stopping unit 3 comprises a series circuit of a push-button switch SW a light source N and a resistor R connected across the resistor R a pair of photoconductve cells CdS, and CdS selectively connectable with a change-over switch SW and shutters S, and S associated with the respective photoconductive cells CdS, and CdS The push-button switch SW which may be disposed on the body of the sewing machine, is normally kept in closed position and is urged to open position in response to the depression of the push button. The movable contact of the change-over switch SW is connected with the circuit connecting the junction point of the resistor R and the rectifier SR, with the terminal 0 of the terminal block 1. One of the terminals of the photoconductive cell CdS, is connected with one of the stationary contacts X of the changeover switch SW while one of the terminals of the photoconductive cell CdS is connected with the other stationary contact Y of the change-over switch SW,,, and the other terminal of the photoconductive cells CdS, and CdS is connected with the brush 8,. The photoconductive cells CdS, and CdS in the needle stopping unit 3 are optically coupled to the light source N and the shutters S, and S are disposed between the light source N and the respective photoconductive cells CdS, and CdS These shutters S, and S are mounted at symmetrical positions on a rotary or reciprocating member of the machine.

A lamp L in the sewing machine is connected between the brush B, and the anode of the silicon controlled rectifier SCR. A series circuit of a trimmer resistor VR a resistor R and an on-off switch SW terminates in a terminal d of the terminal block 1 and is branched from the circuit connecting the junction point of the resistor R and the rectifier SR with the terminal of the terminal block 1. A resistor R is connected at one end with the anode of the silicon controlled rectifier SCR and at the other end with the onoff switch SW A controller unit 2 comprises a photoconductive cell CdS a light source N an on-off switch SW arranged for interlocking operation with a shutter S, and resistors R and R The resistor R is connected at one end with the terminal d of the terminal block 1 and at the other end with one terminal of the photoconductive cell CdS which is connected at the other terminal with the terminal c of the terminal block 1. The resistor R is connected at one end with the terminal b of the terminal block 1 and at the other end with one terminal of the light source N, which is connected at the other terminal with one end of the resistor R The switch SW is connected between one end of the resistor R and the corresponding end of the resistor R The switch SW is arranged for interlocking operation with the shutter S in such a manner that it is urged to open position in response to the operation of the shutter S, while it is kept in closed position when the shutter S is not actuated.

In operation, when an ac. voltage is applied across the power supply terminals E and E and the main switch SW is urged to the closed position in the nonoperating state of the shutter S in the controller unit 2, that is, in the state in which the switch SW is kept in the closed position, current is supplied to the circuit which is traced from one of the power supply terminals E main switch SW lamp L to the other power supply terminal E thereby energizing the lamp L. Current is also supplied to the circuit which is traced from the power supply terminal E main switch SW -resistor R, on-off switch SW (normally kept in the closed position)resistor R trimmer resistor VR -,rectifier SR resistor R -brush B armature A-brush B, to the other power supply terminal E and to the circuit which is traced from the power supply terminal E main switch SW resistor R -switch SW resistor R trimmer resistor VR resistor R -trimmer resistor VR variable resistor VR resistor R brush B armature A-brush B to the power supply terminal E the current passing through this circuit being further shunted from the variable resistor VR, to the power supply terminal E through resistor R Further, current is supplied to the circuit which is traced from the power supply terminal E --main switch SW,-resistor R -mean lamp N, to the power supply terminal E, thereby energizing the neon lamp N,. Furthermore, current is supplied to the circuit which is traced from the power supply terminal E resistor R rectifier SK -capacitor c,-main switch SW, to the power supply terminal E and to the circuit which is traced from the power supply terminal E,-resistor R -rectifier SR resistor R resistor R -switch SW associated with the shutter Sresistor R main switch SW to the power supply terminal E Due to the supply of current to the last-mentioned circuit, a voltage required for energizing the light source N in the needle stopping unit 3 appears across the resistor R thereby energizing the light source N in the needle stopping unit 3. On theother hand, the light source N in the controller unit 2 is kept in the deenergized state due to the fact that the switch SW arranged for interlocking operation with the shutter S is kept in the closed position and no current flows through the light source N Due to the flow of current in the manner above described, a voltage appears across the resistor R and trimmer resistor VR to be applied to the gate of the silicon controlled rectifier SCR through the rectifier SR However, the silicon controlled rectifier SCR does not conduct and the motor M is not started since the circuit is designed so that the voltage above described is lower than the firing voltage for the silicon controlled rectifier SCR. Further, in this case, the light source N, in the needle stopping unit 3 has been energized and the shutter S does not intercept the path of light from the light source N toward the photoconductive cell CdS Therefore, the resistance of the photoconductive cell CdS, is reduced to its minimum value and the circuit connecting the junction point of the resistor R and the rectifier SR, with the terminal 0 of the terminal block 1 is shorted to the power supply terminal E through the change-over switch SW (whose movable contact is in contact with the stationary contact X) and the photoconductive cell CdS As a result, no current is supplied to the gate of the silicon controlled rectifier SCR and the silicon controlled rectifier SCR does not conduct.

Then, when the controller unit 2 is actuated to actuate the shutter S, the switch SW arranged for interlocking operation with the shutter S is urged to the open position thereby energizing the light source N Current flows through the circuit which is traced from the power supply terminal El -resistor R rectifier SR resistor R resistor R-,resistor R -light source N resistor R, main switch SW to the power supply terminal E The resistance against the current flowing through this circuit is increased due to the fact that it flows through the resistor R and light source N and the current value becomes smaller than when the switch SW arranged for interlocking operation with the shutter S is in its closed position. Thus, the voltage across the resistor R is reduced to deenergize the light source N, in the needle stopping unit 3. As the shutter S is gradually moved away from the path of light from the light source N toward the photoconductive cell CdS the amount of light received by the photoconductive cell CdS; is increased to reduce the resistance of the photoconductive cell CdS Therefore, a higher voltage appears across the CdS Therefore, a higher voltage appears across the resistor R and trimmer resistor VR, and this voltage has a substantially constant peak value due to the discharge action of the neon lamp N In other words, a voltage having a waveform as shown by a in FIG. 2 is applied to the gate of the silicon controlled rectifier SCR with the result that the silicon controlled rectifier SCR conducts and the motor M is started. In FIG. 2, curve a is a waveform of the charge voltage across the capacitor C connected between the gate and cathode of the silicon controlled rectifier SCR, and curve b is a waveform of the voltage across the neon lamp N The number of revolutions or rotational speed of the motor M can be varied by varying the relative position of the shutter S intercepting the path of light from the light source N toward the photoconductive cell CdS hence by varying the resistance value of the photoconductive cell CdS The function of the variable resistor VR is to determine the maximum number of revolutions of the motor M.

With the rotation of the motor M due to the conduction of the silicon controlled rectifier SCR, the shutters S and S mounted at the symmetrical positions on the rotary or reciprocating member of the machine intercept cyclically the path of light from the light source N toward the photoconductive cells CdS and CdS the cycle of intercepting the light path being dependent upon the number of revolutions of the motor M at which the motor M is rotating at this time.

When the force of depression imparted to the controller unit 2 is released to return the shutter S to the original position in which it intercepts the path of light from the light source N toward the photoconductive cell CdS again, the resistance of the photoconductive cell CdS increases to the maximum value again. The switch SW arranged for interlocking operation with the shutter S is urged to the closed position thereby cutting off the current supplied to the light source N; with the result that the light source N having been energized is now deenergized. The motor M is restored to the original or inoperative state again and ceases to rotate. However, the rotary or reciprocating member of the machine continues to make rotary or reciprocating movement for a short period of time due to the inertia until finally it is completely stopped at the position at which the shutter S does not intercept the path of light from the light source N toward the photoconductive cell CdS anymore and the resistance of the photoconductive cell CdS is reduced to its minimum value.

When the movable contact of the change-over switch SW is brought into contact with the stationary contact Y connected to the photoconductive cell CdS after the motor M has been stopped in the manner above described, the gate voltage supplied from the circuit including the photoconductive cell CdS attains a triggering level due to the fact that the shutter S intercepts the path of light from the light source N toward the photoconductive cell CdS and the resistance of the photoconductive cell CdS is maximum. Due to the application of such gate voltage to the silicon controlled rectifier SCR, it conducts to start the motor M again. However, the motor M ceases to rotate when the shutter S is moved to the position at which it does not intercept the path of light from the light source N toward the photoconductive cell CdS and the machine ceases to operate at this position.

When the change-over switch SW is thrown to the position to connect the photoconductive cell CdS, to the gate current control circuit for the silicon controlled rectifier SCR, the sewing needle of the electric sewing machine can be stopped at its upper position by arranging the shutter S, on the rotating or reciprocating member of the machine so that the position of the shutter at which it does not intercept the path of light from the light source N toward the conductive cell CdS corresponds to the needle upper position. Then, when the change-over switch SW is changed over to the position to connect the photoconductive cell CdS with the gate current control circuit for the silicon controlled rectifier SCR after the motor M has been stopped, the motor M is energized for a very short length of time and the needle is stopped at its lower position. Further, the push-button switch SW may be depressed to deenergize the light source N in the state in which the motor M is in its stopped position and the path of light from the light source N toward one of the photoconductive cells CdS and CdS connected in parallel between the gate current control circuit for the silicon controlled rectifier SCR and the power supply terminal E is intercepted by the associated shutter S or S In this case, the photoconductive cell CdS has its maximum resistance value, and a large current flows through the resistor R trimmer resistor VR variable resistor VR,, and resistors R and R connected across the gate and cathode of the silicon controlled rectifier SCR. Thus, a high voltage appears across the cathode and gate of the silicon controlled rectifier SCR and is applied to the gate to trigger the silicon controlled rectifier SCR so that the latter conducts. The motor M is rotated at a low speed corresponding to the minimum number of revolutions determined by the resistance values of the trimmer resistors VR and VR until the force imparted to the switch SW is released and the shutter S is moved to the position at which it does not intercept the path of light from the light source N toward the photoconductive cell CdS The motor M is stopped at this position. Further, when the push-button switch SW is kept depressed, the motor M is rotated at the low speed until the needle is stopped at the predetermined position. Furthermore, when the on-off switch SW is urged from the closed to the open position in the inoperative state of the sewing machine, no current is supplied to the circuit including the resistor R trimmer resistor VR rectifier SR resistor R brush B armature A and brush B to the circuit including the resistor R trimmer resistor VR variable resistor VR,, and resistors R and R and to the circuit including the changeover switch SW and photoconductive cells CdS and CdS and the motor M would not rotate even when the change-over switch SW is changed over or when the push-button switch SW is depressed. The motor M starts to rotate again in response to the actuation of the controller unit 2, and the needle can be stopped at any desired position when the force imparted to the controller unit 2 is released to stop the motor M. It will thus be seen that the actuation of the controller unit 2 in the closed position of the onoff switch SW actuates the needle stopping unit 3 so as to automatically stop the needle at its upper or lower position, while the actuation of the controller unit 2 in the open position of the on-off switch SW causesrotation of the motor M independently of the operation of the needle stopping unit 3.

It will be understood from the foregoing description that the sewing needle of the electric sewing machine can be automatically stopped at a predetermined position such as an upper or lower position in response to the stoppage of the machine during the sewing operation or upon completion of the sewing operation. Further, depression and subsequent release of the pushbutton switch SW while the needle is in the stopped position causes rotation of the motor at a constant low speed and the needle can make one reciprocating movement from its upper or lower stopped position to return to the original stopped position again. Furthermore, continuous depression of the push-button switch SW causes movement of the needle at the constant low speed until the needle is stopped at its upper or lower position by the release of said push-button switch. Therefore, one or more further stitches as desired can be effected at low speed. Moreover, when the on-off switch SW is turned off and the flywheel is turned by hand,'the needle stopping means is cut off from the power supply and the needle actuating mechanism is rotated manually without being rotated by the action of the needle stopping means. This is advantageous, for example, for effecting initial winding of the thread to the bobbin and eliminates an undesirable feeling of unrest for the sewer.

When the controller unit 2 is depressed to accuate the shutter S, with the switch SW in its off position, the motor is actuated to operate the machine, and by the release of the controller unit 2, the needle can be stopped at any desired position. According to the present invention, the sewing operation can be carried out speedily with simple manipulation.

I claim:

1. A system for automatically stopping the needle of a sewing machine at a predetermined position comprising control circuit means including a semiconductor control element for controlling the operation of a commutator motor driven by an ac. power supply; a needle stopping means coupled to said control circuit means, for stopping the needle at the predetermined position, said needle stopping means comprising a light source, a plurality of photoconductive cells optically coupled to said light source, a push-button switch means connected in series with said light source, a change-over switch means selectively connectable with said photoconductive cells, and a plurality of shutters mounted on a rotary or reciprocating member of the sewing machine movable in response to the operation of the motor, said shutters being arranged to cyclically intercept the path of light from said light source toward said photoconductive cells; speed controller means coupled to control circuit means for controlling the speed of said motor; a power supply for supplying power to said system and a switch means coupled to said needle stopping means for disconnecting said needle stopping means from said power supply said switch means having two positions such that, in one of the two positions, the needle can be stopped at the predetermined position, and in the other position, the needle can be stopped at any desired position independently of the operation of said needle stopping means.

2. A system for automatically stopping the needle of a sewing machine at a predetermined positiion comprising control circuit means including a semiconductor control element for controlling the operation of a commutator motor driven by an ac. power supply; a needle stopping means coupled to said control circuit means, for stopping the needle at the predetermined position; speed controller means coupled to control circuit means for controlling the speed of said motor wherein said speed controller means comprises a photoconductive cell, a light source, a shutter disposed movably between said light source and said photoconductive cell for regulating the amount of light directed from said light source toward said photoconductive cell, and a switch means arranged for interlocking operation with said shutter; a power supply for supplying power to said system and switch means coupled to said needle stopping means for disconnecting said needle stopping means from said power supply said switch means having two positions such that, in one of the two positions, the needle can be stopped at the predetermined position, and in the other position, the needle can be stopped at any desired position independently of the operation of said needle stoppings means.

3. A system as claimed in claim 1, wherein said controller means comprises a photoconductive cell, a light source, a shutter disposed movably between said light source and said photoconductive cell for regulating the amount of light directed from said light source toward said photo-conductive cell, and a switch means arranged for interlocking operation with said shutter. 

1. A system for automatically stopping the needle of a sewing machine at a predetermined position comprising control circuit means including a semiconductor control element for controlling the operation of a commutator motor driven by an a.c. power supply; a needle stopping means coupled to said control circuit means, for stopping the needle at the predetermined position, said needle stopping means comprising a light source, a plurality of photoconductive cells optically coupled to said light source, a push-button switch means connected in series with said light source, a change-over switch means selectively connectable with said photoconductive cells, and a plurality of shutters mounted on a rotary or reciprocating member of the sewing machine movable in response to the operation of the motor, said shutters being arranged to cyclically intercept the path of light from said light source toward said photoconductive cells; speed controller means coupled to control circuit means for controlling the speed of said motor; a power supply for supplying power to said system and a switch means coupled to said needle stopping means for disconnecting said needle stopping means from said power supply said switch means having two positions such that, in one of the two positions, the needle can be stopped at the predetermined position, and in the other position, the needle can be stopped at any desired position independently of the operation of said needle stopping means.
 2. A system for automatically stopping the needle of a sewing machine at a predetermined positiion comprising control circuit means including a semiconductor control element for controlling the operation of a commutator motor driven by an a.c. power supply; a needle stopping means coupled to said control circuit means, for stopping the needle at the predetermined position; speed controller means coupled to control circuit means for controlling the speed of said motor wherein said speed controller means comprises a photoconductive cell, a light source, a shutter disposed movably between said light source and said photo-conductive cell for regulating the amount of light directed from said light source toward said photo-conductive cell, and a switch means arranged for interlocking operation with said shutter; a power supply for supplying power to said system and switch means coupled to said needle stopping means for disconnecting said needle stopping means from said power supply said switch means having two positions such that, in one of the two positions, the needle can be stopped at the predetermined position, and in the other position, the needle can be stopped at any desired position independently of the operation of said needle stoppings means.
 3. A system as claimed in claim 1, wherein said controller means comprises a photoconductive cell, a light source, a shutter disposed moVably between said light source and said photoconductive cell for regulating the amount of light directed from said light source toward said photo-conductive cell, and a switch means arranged for interlocking operation with said shutter. 